1. Technical Field of the Invention
The present invention relates generally to a radar system which may be employed in anti-collision devices for moving objects such as automotive vehicles to monitor the position of a target present within a detectable zone and an aperture antenna used in such a radar system.
2. Background of Related Art
Monopulse radars are known as being suitable for anti-collision devices for moving objects.
Typical monopulse radars are designed to receive a radar beam reflected from a target concurrently through a pair of antennas arranged close to each other to determine the azimuth angle of the target based on a phase difference between received signals and amplitude thereof. The monopulse radars, however, have the drawback in that the radar beam has the directivity, so that a detectable zone of the azimuth angle of the target is limited to a narrow area where antenna-received beams overlap with each other.
For example, an automotive radar system requires quick detection of a vehicle which has cut in front of a radar-equipped vehicle and accurate detection of obstacles present on or near a road. Such detection, however, becomes difficult especially when the radar-equipped vehicle is traveling on a curved road. It is, thus, sought to widen further the detectable zone of the radar system.